Particle abrasion

K = Constant (depends on target material, particle abrasiveness and size distribution)... 

The constant, K, depends on the target material, particle abrasiveness, and size distribution of the particles. The kinetic energy of the particles is Mp x Vp + 2. This parameter includes the solids loading, or concentration, and velocity of the particle. Alpha is the angle of impingement of the particle on the blade surface. 

Conti, R. and Nienow, A.W., 1980. Particle Abrasion at High Solids Concentration in Stirred Vessels - II. Chemical Engineering Science, 35, 543-547. 

Nienow, A.W. and Conti, R., 1978. Particle abrasion at high solids concentration in stirred vessels. Chemical Engineering Science, 33, 1077-1086. 

Despite the little experimental data, there are two models available in the literature. Adams etal. (1992) considered dense phase conveying. They tried to predict the amount of attrition as a function of conveying distance by coupling a Monte Carlo simulation of the pneumatic conveying process with data from single-particle abrasion tests. Salman et al. (1992) focused on dilute phase conveying. They coupled a theoretical model that predicts the particle trajectory with single particle impact tests (cf. Mills, 1992). 

Because of the random motion of the solids, some abrasion of the surface occurs in the bed. However, this abrasion is very small relative to the particle breakup caused by the high-velocity jets at the distributor. Typically, particle abrasion (fragmentation) will amount to about 0.25 to 1 percent of the solids per day. In the area of high gas velocities at the distributor, greater rates of attrition will occur because of fracture of the particles by impact. As mentioned above, particle fracture of the grid is reduced by adding shrouds to the gas distributor. 

A detailed discussion of crystallizer design and secondary nucleation is beyond the scope of this chapter but the problem has been considered for a wide range of conditions by Randolph and Larson and some simple and idealized cases have been treated in great detail by Larson and Garside However, the points to be made in this chapter about reaction rates apply also to crystal growth rates and in addition a few comments on the effect of agitation on secondary nucleation and particle abrasion are included. 

Combination of abrasion and corrosion is also called corrosive-abrasive wear. Particle abrasion with low pressure between the particles and the material surface is closely related to particle erosion at low impact angles. Corrosive-abrasive wear has... 

Measurement of the pressure loss across the adsorber provides information on particle abrasion and blockages in the support tray. 

Attrition rates are usually less than 1 -3% per year. The actual rate will depend on carbon hardness. Particle abrasion and the resulting bed compaction leads to an increased pressure loss after several years of service. After 3-5 years of service screening to its original size is necessary. 

Thus, the crosslinked biodegradable material acts as a matrix for embedded abrasive particles. Abrasive particles are listed in Table 10.3. 

Cell death rate oc microcarrier size (particle abrasion is proportional to (d ) Nienow (2006))... 

The coUision/impact caused cell damage proposition of Cherry and Papoutsakis (1986) is also supported by Nienow (2006). It has been mentioned earlier that particle abrasion is proportional to This observation indicates that smaller size microcarrier beads should decrease the impact force. Cherry and Papoutsakis (1989a, b)... 

Structured and porous particles Abrasion resistance Higher oil absorption HO2 extension... 

There are many types of abrasion resistance tests for specific forms of abrasive materials and for specific applications and materials. The abrasives used in these tests include loose particle abrasives (ASTM D673 and D1242), abrasives bonded on cloth or paper (ASTM D1242), and standard abrasive wheels (ASTM D1044). ASTM D1044 evaluates the resistance of transparent plastics to surface abrasion by... 

Resistance Erosion occurs when refractory comes in contact with metal and gas carrying dust and slag particles. Abrasion resistance of refractory is increased by using denser (low porosity), fine grained and wear resistant refractory materials. 

Nienow and Conti (1978) developed a model of particle abrasion at high solids concentration based on Rittinger s law of comminution. When tested experimentally using copper sulphate and nickel ammonium sulphate crystals in two non-solvent liquids, measured abrasion rates were consistent with a second-order dependence of concentration as predicted (Figure 5.12). 

Erosion of internals, pipes, and vessels from particle abrasion can be severe. 

Microabrasion corrosion is the degradation of the material by the combined action of particle abrasion, mechanical load and corrosivity of the medimn (Gee et al, 2003 Staek and Mathew, 2003 Stack et al, 2005). Microabrasion corrosion is cotmnonly observed in orthopedic implants, particularly on hip joints (Sinnett-Jones et al, 2005 Bello et al, 2007 Sun et al, 2009a, 2009b Stack et al, 2010b). 

The comparison with experimental results has shown that the proposed approach allows one to compare and evaluate the relative role of factors such as chemical stability of oxides, particle abrasivity, metal dissolution rate, metal ductility, metal embritdement by oxide films. In particular the approach suggests that when the metal is subject to dissolution third bodies are not likely to form and therefore the system behaves as a two bodies system. When stable metal oxide form, the system behaviour depends more on the third body behaviour (oxidation, abrasivity) and on the probability for a particle to get ejected fi-om the contact (system dependent vibration and geometry). The... 

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